Django migrations directly import custom fields?

[Greg]

Hi all,

I'm moving over to the new migrations, and I've noticed whenever I
create a migration involving a custom model field, it imports that field
at the top of the migration. The south docs were always quite firm about
not doing this sort of thing, in case the code changed in the future. Is
this a design decision, i.e. we now expected to make sure imports in our
migration files always work in the future? What are the reasons for
this? I can imagine this causing issues when refactoring old code for
example.

If this is more a question for django-developers, let me know and I'll
post it there.

Thanks,
Greg